International audienceThe efficiency of organometal- (Ti, Zr, Sn, Hf, and Bi) and metal oxide- (Ge and Sb) based catalysts was investigated during the transesterification step of the synthesis of poly(butylene succinate) (PBS). PBS was prepared from succinic acid and 1,4-butanediol via a two-stage melt polycondensation process. The catalytic efficiency of the organometal catalysts was as follows: Ti≫Zr∼ Sn>Hf>Sb>Bi. The germanium and antimony metal oxides displayed desirable catalytic efficiency when were associated with hydroxy acids (lactic acid or glycolic acid), which acted as chelating agents. However, this catalytic system exhibited lower efficiency compared to the titanium system. Furthermore, at high concentrations of hydroxy acids the overall transesterification rate decreased. This effect can be explained by the substitution of PBS hydroxyl end groups by a lactic or glycolic unit, both of which are less reactive during the transesterification reaction. The role of catalytic residues during the storage and processing of PBS was also studied. The reduced viscosity of the PBS samples did not vary when processing at 190 °C from 1 to 10 minutes. However, when stored under ambient conditions, all PBS samples were prone to significant hydrolytic degradation, especially those containing a titanium catalyst. This behavior indicates that zirconium- and germanium-based catalysts could be interesting substitutes for titanium-based catalysts
This work is dedicated to Dr. Alain Michel for his retirement and in memory of Prof. Morand Lambla. Dr. Michel and Prof. Lambla were the pioneers of the development of reactive processing in FranceThe review is devoted to the fundamental aspects of the reactive processing of thermoplastic polymers. First of all, some reactive processing examples, including polymer grafting (vinyl silane, maleic anhydride) and/or functionalization, bulk polymerization (urethane, lactams, acrylate, e-capolactone), polyester modification and new copolymers synthesis, are presented. From a fundamental point of view, the review covers the state of the art in the domains of rheology (specifically modelling of rheo-kinetics), diffusion and mixing in highly viscous reactive or non reactive media. Finally, 1, 2 and 3-D simulation of the reactive extrusion process in twin-screw extruder is reported at the end of the review.
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